Spruce budworm elastase precipitates Bacillus thuringiensis delta-endotoxin by specifically recognizing the C-terminal region

Citation
R. Milne et al., Spruce budworm elastase precipitates Bacillus thuringiensis delta-endotoxin by specifically recognizing the C-terminal region, INSEC BIO M, 28(12), 1998, pp. 1013-1023
Citations number
37
Categorie Soggetti
Entomology/Pest Control","Biochemistry & Biophysics
Journal title
INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY
ISSN journal
09651748 → ACNP
Volume
28
Issue
12
Year of publication
1998
Pages
1013 - 1023
Database
ISI
SICI code
0965-1748(199812)28:12<1013:SBEPBT>2.0.ZU;2-9
Abstract
A gut juice protein from Choristoneura fumiferana (spruce budworm) larvae t hat precipitates certain delta-endotoxins shows a unique specificity for th e C-terminal amino acid sequence. Using homolog scanning mutants, we have i dentified a contiguous region of the Cry1Aa toxin which interacts with the 75-kDa toxin precipitating protein (TPP-75)(1) resulting in precipitation. The contiguous region from Cry1Aa can be transferred to Cry1Ac and results in an identical precipitation reaction. The precipitation reaction occurs r apidly and is unique in that the ratio of precipitating protein to toxin is low (estimated at 0.01), unlike antibody-antigen reactions which exhibit m ole ratios close to 1. TPP-75 has been characterized as an elastase-like se rine protease. We have taken advantage of this serine protease character an d incorporated a radiolabel using an irreversible inhibitor. The radiolabel has allowed us to show the coincidence of the catalytically-inhibited TPP- 75 with the toxin in a blotting assay and to follow the degradation of TPP- 75 during storage. TPP-75 represents the first evidence that gut juice prot eins may selectively attenuate the activity of delta-endotoxins, prior to b inding to putative receptors on susceptible cells. TPP-75 should be evaluat ed as a possible resistance mechanism for those larvae that do not exhibit a receptor-based resistance. (C) 1998 Elsevier Science Ltd. All rights rese rved.